排序方式: 共有33条查询结果,搜索用时 31 毫秒
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Svenja M. Ackermann Dirk W. Lachenmeier Thomas Kuballa Birk Schütz Manfred Spraul Mirko Bunzel 《Magnetic resonance in chemistry : MRC》2019,57(9):579-588
Both the German and European organic food markets are growing fast, and there is also a rising demand for organic chicken eggs. Consumers are willing to pay higher prices for organic eggs produced in an animal-appropriate environment considering animal welfare. Strict labelling requirements do not prevent chicken eggs from being a subject of food fraud. Conventionally produced (barn/free-range) eggs can easily be mislabeled as organic eggs. Especially because the demand for organically produced chicken eggs is likely to exceed supply in the future, mislabeling appears to be a realistic scenario. Therefore, there is a need for analytical methods that are suitable to classify eggs as being either conventionally or organically produced. Nuclear magnetic resonance (NMR) spectroscopy in combination with multivariate data analysis is a suitable tool to screen eggs according to the different systems of husbandry. Sample preparation is based on a fat extraction method, which was optimised for application to freeze-dried egg yolk. Samples were analysed using typical q-NMR parameters. A nontargeted approach was used for the analysis of the 1H NMR data. Principal component analysis (PCA) was applied followed by a linear discriminant analysis (PCA-LDA) and Monte Carlo cross-validation. In total, 344 chicken eggs (214 barn/free-range eggs and 130 eggs from organic farms), most of them originating from Germany, were used to build and validate the prediction model. The results showed that the prediction model allowed for the correct classification of about 93% of the organic eggs. 相似文献
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Consonni R Cagliani LR Benevelli F Spraul M Humpfer E Stocchero M 《Analytica chimica acta》2008,611(1):31-40
This work presents the capability of NMR spectroscopy combined with Chemometrics in predicting the ageing of Balsamic and Traditional Balsamic Vinegar of Modena. The need of an analytical method is an important requirement for both research oriented and commercial evaluation of these very valuable products. 1H NMR spectroscopy, based on the advantage of rapid sample analysis without any manipulation or derivatization, is here proposed as a valid tool to describe Balsamic and Traditional Balsamic Vinegar of Modena. For this purpose, 72 reliable samples, were divided into three different groups according to their ageing process: young (<12 years), old (>12 and <25 years) and extra old (>25 years). Hierarchical Projection to Latent Structures Discriminant Analysis (PLS-DA) allowed us to characterize the ageing process. Variables showing the largest VIP (Variable Importance in the Projection) were extracted from PLS-DA model, thus shedding lights onto the role played by specific compounds in this complex ageing process. Two robust classification models, were built by PLS-DA and Naïve Bayes classifier and compared to prove the accuracy of the representation on both training and test sets. The predictions obtained for 41 “unknown” vinegar samples with these both methods gave more than 80% agreement among them. 相似文献
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Sturm S Seger C Godejohann M Spraul M Stuppner H 《Journal of chromatography. A》2007,1163(1-2):138-144
Identification of putative biomarker molecules within the genus Corydalis (Papaveraceae) was pursued by combining conventional off-line sample enrichment with high-performance liquid chromatography-solid phase extraction-nuclear magnetic resonance (HPLC-SPE-NMR) based structure elucidation. Off-line reversed phase solid phase extraction (SPE) was used to enrich the desired analytes from a methanolic extract (93 mg dry weight) of a miniscule single tuber (233 mg dry weight) of C. solida. An aliquot of the SPE fraction (2.1 mg) was subjected to separation in the HPLC-SPE-NMR hyphenation. Chromatographic peaks bearing the metabolites under investigation were trapped in the SPE device in a single experiment and transferred to a 600 MHz NMR spectrometer equipped with a 30 microl cryofit insert fed into a 3 mm cryoprobe. Recorded homo- and heteronuclear 1D and 2D NMR data allowed the identification of the three analytes under investigation as protopine, allocryptopine, and N-methyl-laudanidinium acetate. The latter is a rare alkaloid, which has been isolated only once before. 相似文献
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Two approaches to NMR analysis of mixtures used in Bruker instruments are considered: (1) a combination of high-performance liquid chromatography, NMR, and mass spectrometry, (2) the use of specialized software and spectral databases. 相似文献
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Klaus Albert Ulrich Braumann Roman Streck Manfred Spraul Rainer Ecker 《Analytical and bioanalytical chemistry》1995,352(5):521-528
The separation of monomeric acrylates was performed with High Performance Liquid Chromatography (HPLC) and Supercritical Fluid Chromatography (SFC). A direct on-line structural assignment of all compounds by continuous-flow 1HNMR spectroscopy is possible with both separation techniques. The direct SFC-NMR coupling offers the advantage that the recorded continuous-flow 1HNMR spectrum is not obscured by solvent signals. 相似文献
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Schefer AB Braumann U Tseng LH Spraul M Soares MG Fernandes JB da Silva MF Vieira PC Ferreira AG 《Journal of chromatography. A》2006,1128(1-2):152-163
Separation and characterization of limonoids from Switenia macrophylla (Meliaceae) by HPLC-NMR technique has been described. Analyses were carried out using reversed-phase gradient HPLC elution coupled to NMR (600 MHz) spectrometer in stopped-flow mode. Separated peaks were collected into an interface unit prior to NMR measurements, which were performed with suppression of solvent signals by shaped pulses sequences. Structure elucidation of the limonoids was attained by data obtained from 1H NMR, TOCSY, gHSQC and gHMBC spectra without conventional isolation that is usually applied in natural products studies. 相似文献
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Klaus Albert Ulrich Braumann Roman Streck Manfred Spraul Rainer Ecker 《Fresenius' Journal of Analytical Chemistry》1995,352(5):521-528
The separation of monomeric acrylates was performed with High Performance Liquid Chromatography (HPLC) and Supercritical Fluid Chromatography (SFC). A direct on-line structural assignment of all compounds by continuous-flow 1HNMR spectroscopy is possible with both separation techniques. The direct SFC-NMR coupling offers the advantage that the recorded continuous-flow 1HNMR spectrum is not obscured by solvent signals.Dedicated to Professor Dr. H. Kriegsmann on the occasion of his 70th birthday 相似文献
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Spraul BK Suresh S Glaser S Perahia D Ballato J Smith DW 《Journal of the American Chemical Society》2004,126(40):12772-12773
Hexa-peri-hexabenzocoronene (HBC) derivatives possess many interesting properties ranging from liquid crystallinity, to hole transport, to variable emission behavior, yet are plagued by insolubility and general accessibility of polymerizable substituents. The first synthesis of trifluorovinyl ether-substituted hexabenzocoronene and its polymerization to perfluorocyclobutyl (PFCB) polymers and copolymers is shown. Unlike hydrocarbon ethers, fluoro vinyl ethers are stable under HBC oxidation conditions. Discrete HBC units in PFCB polymers provide access to potentially processable HBC optical materials. 相似文献